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.TH TCFLOW 3C "Aug 14, 2002"
.SH NAME
tcflow \- suspend or restart the transmission or reception of data
.SH SYNOPSIS
.LP
.nf
#include <termios.h>

\fBint\fR \fBtcflow\fR(\fBint\fR \fIfildes\fR, \fBint\fR \fIaction\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBtcflow()\fR function suspends transmission or reception of data on the
object referred to by \fIfildes\fR, depending on the value of \fIaction\fR. The
\fIfildes\fR argument is an open file descriptor associated with a terminal.
.RS +4
.TP
.ie t \(bu
.el o
If \fIaction\fR is \fBTCOOFF\fR, output is suspended.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIaction\fR is \fBTCOON\fR, suspended output is restarted.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIaction\fR is \fBTCIOFF\fR, the system transmits a \fBSTOP\fR character,
which is intended to cause the terminal device to stop transmitting data to the
system.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If \fIaction\fR is \fBTCION\fR, the system transmits a \fBSTART\fR character,
which is intended to cause the terminal device to start transmitting data to
the system.
.RE
.sp
.LP
The default on the opening of a terminal file is that neither its input nor its
output are suspended.
.sp
.LP
Attempts to use \fBtcflow()\fR from a process which is a member of a background
process group on a \fIfildes\fR associated with its controlling terminal, will
cause the process group to be sent a \fBSIGTTOU\fR signal. If the calling
process is blocking or ignoring \fBSIGTTOU\fR signals, the process is allowed
to perform the operation, and no signal is sent.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBtcflow()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEBADF\fR\fR
.ad
.RS 10n
The \fIfildes\fR argument is not a valid file descriptor.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIaction\fR argument is not a supported value.
.RE

.sp
.ne 2
.na
\fB\fBENOTTY\fR\fR
.ad
.RS 10n
The file associated with \fIfildes\fR is not a terminal.
.RE

.sp
.LP
The \fBtcflow()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEIO\fR\fR
.ad
.RS 7n
The process group of the writing process is orphaned, and the writing process
is not ignoring or blocking \fBSIGTTOU\fR.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe, and Async-Signal-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR tcsendbreak (3C),
.BR termio (4I),
.BR attributes (7),
.BR standards (7)
